/*
 *  SableJBDD, a Java Binary Decision Diagram package.
 *  Copyright (C) 2003  Feng Qian
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
//$Id: AbstractBddCache.java,v 1.1 2004/03/12 00:15:25 fqian Exp $

package SableJBDD.bdd.internal;

import SableJBDD.bdd.JBddConstants;
import SableJBDD.bdd.JBddNode;

import SableJBDD.cache.TripleIntKeyCache;

import SableJBDD.bdd.util.HashFunction;

import java.io.PrintStream;

/**
 * An abstract cache uses three integers as the key.
 *
 * @author Feng Qian
 */
public abstract class AbstractBddCache implements BddCache{
  
  /////////////////////////////////////////////
  // IMPLEMENTATION
  ////////////////////////////////////////
  protected TripleIntKeyCache cacheImpl;
 
  public int size() {return this.cacheImpl.numberOfEntries();}
 
  /**
   * Looks up a bdd node by f, g, and h.
   * Returns null if no such node exists.
   */
  public synchronized JBddNode lookup(Unique f, Unique g, Unique h) {
    int fid = f.getUniqueId(), gid = g.getUniqueId(), hid = h.getUniqueId();
    Object cvalue = cacheImpl.lookup(fid, gid, hid);
    JBddNode node = null;
    if (cvalue != null) {
      node = getNodeOutOfCacheValue(cvalue);
      if (node == null) { // it might be a weak reference
        cacheImpl.invalidate(fid, gid, hid);
      }
    }
    return node;
  }

  /**
   * Puts the ite(f,g,h) in the cache.
   */
  public synchronized void put(Unique f, Unique g, Unique h, JBddNode result) {
    int fid = f.getUniqueId(), gid = g.getUniqueId(), hid = h.getUniqueId();
    Object value = makeCacheValue(result);
    cacheImpl.put(fid, gid, hid, value);
  }

  public void reset() {
    this.cacheImpl.reset();
  }

  protected abstract Object makeCacheValue(JBddNode node);
  protected abstract JBddNode getNodeOutOfCacheValue(Object cvalue);
 
  public void reportStatistics(PrintStream out) {
    this.cacheImpl.reportStatistics(out);
  }
}
